Ink compositions with excellent light resistance

ABSTRACT

An object of the present invention is to provide ink compositions possessing excellent lightfastness. The cyan ink composition according to the present invention comprises, as colorants, a cyan colorant selected from the group consisting of C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, and a mixture of the cyan colorants, and a yellow colorant having a higher fading rate than the cyan colorant. The magenta ink composition according to the present invention comprises, as colorants, a magenta colorant selected from the group consisting of C.I. Pigment Red 122, C.I. Pigment Red 202, C.I. Pigment Red 209, and mixtures of the magenta colorants, and a yellow colorant having a higher fading rate than the magenta colorant.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cyan ink composition and a magentaink composition each possessing excellent lightfastness.

2. Background Art

Ink jet recording printers are becoming widely spread in recent years.Ink jet recording is a printing method wherein droplets of an inkcomposition are ejected and deposited on recording media, such as paper,to perform printing. The feature of the ink jet recording is that imageshaving a combination of high resolution with high quality can be printedat a high speed by means of a relatively inexpensive apparatus. Inparticular, color ink jet recording apparatuses can improve imagequality, can also be utilized as an output device for photographs, andhave also become used, for example, as digital printing machines,plotters, and CAD output devices. The images printed by ink jetrecording printers, which have become widely utilized in this way, areconsidered utilizable in various forms. In particular, for example,photograph-like prints are considered to be placed for display in aplace exposed to light emitted from a fluorescent lamp or directsunlight, for example, in the open for a long period of time. Therefore,lightfastness is a very important property requirement to be satisfiedby records produced by ink jet recording.

In recent years, inks using a pigment as a colorant have become used forimproving the lightfastness of records produced by ink jet recording. Inthe case of color images yielded by pigment-based ink compositions,fading of images can be suppressed even when exposed to light emittedfrom a fluorescent lamp or direct sunlight, for example, in the open fora long period of time. Even in such a case, however, in some cases, thehue of the image undergoes a change, and, consequently, the whole imagebecomes yellowish. For this reason, an ink composition has been desiredthat can yield images which are less likely to be deteriorated evenafter storage for a long period of time, that is, possesses excellentlightfastness.

SUMMARY OF THE INVENTION

The present inventors have now found that, in a cyan ink composition, ayellow colorant having a specific fading rate added in addition to ageneral cyan colorant can suppress a change in hue of printed ink and,consequently, can improve lightfastness of the yielded images. Thepresent inventors have also found that the improvement in lightfastnessof images can also be achieved in the same manner in the case of amagenta ink composition. The present invention has been made based onsuch finding.

Accordingly, it is an object of the present invention to provide an inkcomposition which can realize images possessing excellent lightfastness.

Thus, according to one aspect of the present invention, there isprovided a cyan ink composition comprising, as colorants, a cyancolorant selected from the group consisting of C.I. Pigment Blue 15:3,C.I. Pigment Blue 15:4, and a mixture of said cyan colorants, and ayellow colorant having a higher fading rate than the cyan colorant.

According to another aspect of the present invention, there is provideda magenta ink composition comprising, as colorants, a magenta colorantselected from the group consisting of C.I. Pigment Red 122, C.I. PigmentRed 202, C. I. Pigment Red 209, and mixtures of said magenta colorants,and a yellow colorant having a higher fading rate than the magentacolorant.

According to a further aspect of the present invention, there isprovided an ink set comprising a yellow ink composition, a magenta inkcomposition, and a cyan ink composition, the cyan ink composition beingthe cyan ink composition according to the present invention, the magentaink composition being the magenta ink composition according to thepresent invention.

In the ink compositions according to the present invention, in additionto a colorant commonly added to ink compositions (that is, a cyancolorant or a magenta colorant), a yellow colorant having a higherfading rate than the cyan colorant or magenta colorant is added as thecolorant in the ink compositions. It should be noted that the cyancolorant or the magenta colorant contained as the colorant component inthe ink composition, when exposed to outdoor or other environment afterimage formation, gradually undergoes a change in hue and becomesyellowish. On the other hand, the yellow colorant used in the inkcompositions according to the present invention, when exposed to outdooror other environment after image formation, is faded to render theyellowness of the colorant component low as a whole. Therefore, forexample, when an image is formed using a cyan ink composition containinga cyan colorant and a yellow colorant followed by exposure of the imageto outdoor or other environment, the cyan colorant contained in the inkcomposition yellows with the elapse of time while the yellowness of theyellow colorant is lowered. Consequently, it is considered that therecorded image can hold the original hue of the cyan ink composition andcan form images possessing excellent lightfastness. The same is appliedwith respect to the magenta ink composition. The use of a cyan inkcomposition and a magenta ink composition, which have adopted the aboveconstitution, in an ink set can produce images having betterlightfastness. Further, when the yellow colorant to be used in inkcompositions respectively containing a cyan colorant and a magentacolorant is properly selected while taking into consideration thedifference in fading rate between the cyan colorant and the magentacolorant, the lightfastness of images can be further improved.

DETAILED DESCRIPTION OF THE INVENTION

Ink Compositions

The ink compositions according to the present invention may be used inrecording methods using ink compositions. Recording methods using inkcompositions include, for example, an ink jet recording method, arecording method using writing utensils, such as pens, and other variousprinting methods. Preferably, the ink compositions according to thepresent invention are used in an ink jet recording method.

Cyan Ink Composition

The cyan ink composition according to the present invention basicallycomprises, as colorants, a cyan colorant and a yellow colorant having ahigher fading rate than the cyan colorant. Here the cyan colorant isselected from the group consisting of C.I. Pigment Blue 15:3, C.I.Pigment Blue 15:4, and a mixture of the cyan colorants.

In the present invention, the “fading rate” refers to a rate at which,when a record with ink coated thereon is exposed to light emitted from afluorescent lamp or direct sunlight, for example, in the open for a longperiod of time, the OD value (optical density) of the ink is lowered ascompared with that before the exposure. In general, the fading rate canbe defined by the following equation through the application of apredetermined acceleration test.

Fading rate=100×{(OD value before acceleration test)−(OD value afteracceleration test)}/OD value before acceleration test

“Yellow colorant having a higher fading rate” refers to a yellowcolorant which is more likely to fade than the cyan colorant accordingto the present invention.

Specifically, “that the fading rate of the yellow colorant is higherthan the fading rate of the cyan colorant” means that, preferably, thefading rate value of the yellow colorant in a predetermined accelerationtest for a predetermined period of time (for example, 200 hr) is threetimes or higher than the fading rate value of the cyan colorant, morepreferably the fading rate value of the yellow colorant is 5 times orhigher than the fading rate value of the cyan colorant.

Alternatively, “that the fading rate of the yellow colorant is higherthan the fading rate of the cyan colorant” means that, when a print witha colorant coated thereon is placed under such environmental conditionsas to cause fading, preferably under predetermined acceleration testconditions, the fading time, of the yellow colorant, defined as the timenecessary for the OD value of the print to be lowered by a given rate ispreferably not more than one-third, more preferably not more thanone-fifth, of the fading time of the cyan colorant.

In the present invention, the “predetermined acceleration test” refersto an acceleration test for evaluating a deterioration in quality of animage placed under given conditions for a predetermined period of time,which conditions have been determined by taking into considerationservice conditions, under which the utilization of the print iscontemplated, and a period of time for which the print is placed underthe above service conditions. For example, when the print is placedoutdoors and is exposed to direct sunlight, the predeterminedacceleration test refers to a test in which a deterioration in thequality of an image, when placed outdoors for a predetermined period oftime, is reproduced in a shortened period of time, while, when the printis placed indoors, the predetermined acceleration test refers to a testin which a deterioration in quality of an image, when placed indoors fora predetermined period of time, is reproduced in a shortened period oftime. In general, in the former, light having higher intensity than thelatter is applied, and, when the desired period of time for which theprint is placed is longer, light having higher intensity is exposed fora longer period of time. Further, in the case of an acceleration testfor reproducing a deterioration in the quality of an image, when placedunder special service conditions, such as under high-humidityenvironment, for a desired period of time, the acceleration test refersto an acceleration test in which such special conditions have been takeninto consideration. A specific example of the acceleration test is anacceleration test performed, for example, under the followingconditions, as a test for reproducing, in a shortened period of time, adeterioration in quality of an image under service conditions such thatthe image is allowed to stand for several years in a room having awindow on the south side. That is, accelelation tester: xenonweather-o-meter Ci35A, manufactured by ATLAS; light source: xenon lamp;optical filter: borosilicate glass; irradiation energy: 0.35 W/m² (340nm); black panel temperature: 63° C.; internal temperature of tester:24° C.; and internal humidity of tester: 60%. These conditions may beproperly varied depending upon expected service conditions. For example,an acceleration test may be carried out using a fluorescent lamp of1,000 to 100,000 luxes according to the expected service conditions.

Here “yellow OD value” is an OD value as measured for yellow which hasbeen printed by blotted image printing (100% duty blotted imageprinting) on the so-called “plain paper,” for example, with a MacbethPCM-II tester manufactured by Macbeth.

The yellow colorant used in the cyan ink composition according to thepresent invention may be any yellow colorant so far as the yellowcolorant has a higher fading rate than the cyan colorant. Therefore, anyof dyes and pigments may be used as the yellow colorant. However, theuse of dyes is preferred.

Various dyes, for example, direct dyes, acid dyes, foodstuff dyes, basicdyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes, andreactive disperse dyes, may be used as the dye.

Any of inorganic and organic pigments may be used as the pigment.Inorganic pigments include, in addition to titanium oxide and ironoxide, carbon blacks produced by known processes, such as contact,furnace, and thermal processes. Organic pigments usable herein includeazo pigments (including azo lake, insoluble azo pigment, condensed azopigment, and chelate azo pigment), polycyclic pigments (for example,phthalocyanine, perylene, perinone, anthraquinone, quinacridone,dioxazine, thioindigo, isoindolinone, and quinophthalone pigments),dye-type chelate pigments (for example, basic dye-type chelate pigmentsand acid dye-type chelate pigments), nitro pigments, nitroso pigments,and aniline black.

According to a preferred embodiment of the present invention, thepigment is added, to the ink composition, as a pigment dispersionprepared by dispersing the pigment in an aqueous medium with the aid ofa dispersant or a surfactant. Preferred dispersants include dispersantscommonly used in the preparation of pigment dispersions, for example,polymeric dispersants. It would be apparent to a person having ordinaryskill in the art that the dispersant and the surfactant contained in thepigment dispersion would function also as a dispersant and a surfactantfor the ink composition.

Specific examples of yellow colorants, which are preferred in thepresent invention, include: dyes, such as. C.I. Acid Yellow 23, C.I.Direct Yellow 86, and C.I. Direct Yellow 132; and pigments, such as C.I.Pigment Yellow 13, C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I.Pigment Yellow 83, and C.I. Pigment Yellow 93. The yellow colorant ismore preferably C.I. Acid Yellow 23, C.I. Direct Yellow 86, or C.I.Direct Yellow 132. In the present invention, these yellow colorants maybe used solely or in combination of two or more.

The amount of the cyan colorant in the cyan ink composition added in thepresent invention is preferably about 0.1 to 15% by weight, morepreferably about 0.3 to 4% by weight.

Further, the amount of the yellow colorant used in the cyan inkcomposition according to the present invention may be properly selectedso far as desired lightfastness can be held. Preferably, however, theamount of the yellow colorant added is 0.005 to 0.05% by weight, morepreferably 0.005 to 0.02% by weight, based on the cyan colorant (1% byweight).

Magenta Ink Composition

The magenta ink composition according to the present invention basicallycontains, as colorants, a magenta colorant and a yellow colorant havinga higher fading rate than the magenta colorant. Here the magentacolorant is selected from the group consisting of C.I. Pigment Red 122,C.I. Pigment Red 202, C.I. Pigment Red 209, and mixtures of the magentacolorants.

In the present invention, the “fading rate” and the “predeterminedacceleration test” are as described above.

Further, the “yellow colorant having a higher fading rate” used hereinrefers to a colorant which is more likely to fade than the magentacolorant.

Specifically, “that the fading rate of the yellow colorant is higherthan the fading rate of the magenta colorant” means that, preferably,the fading rate value of the yellow colorant in a predeterminedacceleration test for a predetermined period of time (for example, 200hr) is three times or higher than the fading rate value of the magentacolorant, more preferably, the fading rate value of the yellow colorantis 5 times or higher than the fading rate value of the magenta colorant.

Alternatively, “that the fading rate of the yellow colorant is higherthan the fading rate of the magenta colorant” means that, when a printwith a colorant coated thereon is placed under such environmentalconditions as to cause fading, preferably under predeterminedacceleration test conditions, the fading time, of the yellow colorant,defined as the time necessary for the OD value of the print to belowered by a given rate is preferably not more than one-third, morepreferably not more than one-fifth, of the fading time of the magentacolorant.

The yellow colorant used in the magenta ink composition according to thepresent invention may be selected from those described above inconnection with the yellow colorant used in the cyan ink composition.

The amount of the magenta colorant in the magenta ink composition addedin the present invention is preferably about 0.1 to 15% by weight, morepreferably about 0.5 to 5% by weight.

Further, the amount of the yellow colorant used in the magenta inkcomposition according to the present invention may be properly selectedso far as desired lightfastness can be held. Preferably, however, theamount of the yellow colorant added is 0.005 to 0.05% by weight, morepreferably 0.007 to 0.03% by weight, based on the magenta colorant (1%by weight).

In general, magenta ink is more likely to undergo a change in hue thancyan ink. Therefore, when the cyan ink composition and the magenta inkcomposition are used in combination in an ink set, preferably, theyellow colorant used in the magenta ink composition has a higher fadingrate than, that is, is more likely to fade than, the yellow colorantused in the cyan ink composition.

Other Ink Compositions

According to another aspect of the present invention, there is providedan ink set comprising a yellow ink composition, a magenta inkcomposition, and a cyan ink composition. In this case, the cyan inkcomposition is the cyan ink composition according to the presentinvention, or alternatively, the magenta ink composition is the magentaink composition according to the present invention. Further, both thecyan ink composition and the magenta ink composition in the ink set maybe respectively the cyan ink composition according to the presentinvention and the magenta ink composition according to the presentinvention.

The yellow colorant contained in the yellow ink composition used in theink set according to the present invention may be any yellow colorant sofar as yellow can be printed. In the present invention, a yellow pigmentis preferred.

Further, in the present invention, the ink set comprising the yellow inkcomposition, the magenta ink composition, and the cyan ink compositionmay further comprise a black ink composition. The colorant contained inthe black ink composition usable in the present invention may be anycolorant so far as black can be printed. In the present invention, theuse of a black pigment is preferred.

In the present invention, pigments usable in the yellow ink compositionand the black ink composition include inorganic pigments and organicpigments. Inorganic pigments include, in addition to titanium oxide andiron oxide, carbon blacks produced by known processes, such as contact,furnace, and thermal processes. Organic pigments usable herein includeazo pigments (including azo lake, insoluble azo pigment, condensed azopigment, and chelate azo pigment), polycyclic pigments (for example,phthalocyanine, perylene, perinone, anthraquinone, quinacridone,dioxazine, thioindigo, isoindolinone, and quinophthalone pigments),dye-type chelate pigments (for example, basic dye-type chelate pigmentsand acid dye-type chelate pigments), nitro pigments, nitroso pigments,and aniline black.

According to a preferred embodiment of the present invention, thepigment is added, to the ink composition, as a pigment dispersionprepared by dispersing the pigment in an aqueous medium with the aid ofa dispersant or a surfactant. Preferred dispersants include dispersantscommonly used in the preparation of pigment dispersions, for example,polymeric dispersants. It would be apparent to a person having ordinaryskill in the art that the dispersant and the surfactant contained in thepigment dispersion would function also as a dispersant and a surfactantfor the ink composition.

According to the present invention, the colorant used in the yellow inkcomposition or the black ink composition may be a single type colorantor a mixture of a plurality of types of colorants.

In the ink set according to the present invention, the content of thecolorant in the yellow ink composition is not particularly limited. Thecolorant content, however, is preferably 2 to 15% by weight, morepreferably 3 to 5% by weight, based on the yellow ink composition.

Further, in the present invention, the content of the colorant in theblack ink composition is not particularly limited. The content of thecolorant in the black ink composition, however, is preferably 2 to 15%by weight, more preferably 2 to 8% by weight.

Water, Water-soluble Organic Solvent, and Other Optional Ingredients

According to a preferred embodiment of the present invention, when thecolorant used in these ink compositions is a pigment, this pigment ispreferably added, to the ink composition, as a pigment dispersionprepared by dispersing the pigment in an aqueous medium with the aid ofa dispersant or a surfactant. Preferred dispersants include dispersantscommonly used in the preparation of pigment dispersions, for example,polymeric dispersants.

Examples of preferred dispersants include cationic dispersants, anionicdispersants, and nonionic dispersants. Examples of anionic dispersantsinclude polyacrylic acid, polymethacrylic acid, acrylicacid/acrylonitrile copolymer, vinyl acetate/acrylic ester copolymer,acrylic acid/acrylic alkyl ester copolymer, styrene/acrylic acidcopolymer, styrene/methacrylic acid copolymer, styrene/acrylicacid/acrylic alkyl ester copolymer, styrene/methacrylic acid/acrylicalkyl ester copolymer, styrene/α-methylstyrene/acrylic acid copolymer,styrene/α-methylstyrene/acrylic acid/acrylic alkyl ester copolymer,styrene/maleic acid copolymer, vinylnaphthalene/maleic acid copolymer,vinyl acetate/ethylene copolymer, vinyl acetate/fatty acid vinylethylenecopolymer, vinyl acetate/maleic ester copolymer, vinyl acetate/crotonicacid copolymer, and vinyl acetate/acrylic acid copolymer. Examples ofanionic surfactants include sodium dodecylbenzenesulfonate, sodiumlaurylate, and ammonium salt of polyoxyethylene alkyl ether sulfates.Examples of nonionic surfactants include polyoxyethylene alkyl ethers,polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acidesters, polyoxyethylene alkylphenyl ethers, polyoxyethylenealkylamines,and polyoxyethylene-alkylamides. They may be used alone or in acombination of two or more. According to a preferred embodiment of thepresent invention, a water-soluble styrene-(meth)acrylic acid resin isutilized as a dispersant. In the ink compositions according to thepresent invention, water or a mixed solution composed of water and awater-soluble organic solvent is suitable as a main solvent. Water maybe pure water obtained by ion exchange, ultrafiltration, reverseosmosis, distillation or the like, or ultrapure water. Further, water,which has been sterilized, for example, by ultraviolet irradiation or byaddition of hydrogen peroxide, is preferred because, when the inkcomposition is stored for a long period of time, it can prevent thegrowth of mold and bacteria.

Examples of water-soluble organic solvents include high-boiling organicsolvents. High-boiling organic solvents function to prevent the inkcomposition from drying and consequently to prevent head clogging.Examples of preferred high-boiling organic solvents include: polyhydricalcohols, such as ethylene glycol, diethylene glycol, triethyleneglycol, polyethylene glycol, polypropylene glycol, propylene glycol,butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol,glycerin, trimethylolethane, and trimethylolpropane; alkyl ethers ofpolyhydric alcohols, such as ethylene glycol monoethyl ether, ethyleneglycol monobutyl ether, diethylene glycol monomethyl ether, diethyleneglycol monoethyl ether, diethylene glycol monobutyl ether, triethyleneglycol monomethyl ether, triethylene glycol monoethyl ether, andtriethylene glycol monobutyl ether; urea; 2-pyrrolidone andN-methyl-2-pyrrolidone; 1,3-di-methyl-2-imidazolidinone; andtriethanolamine. The amount of the high-boiling organic solvent added isnot particularly limited. The amount of the high-boiling organic solventadded, however, is preferably about 0.5 to 40% by weight, morepreferably about 2 to 20% by weight.

Further, the ink compositions may contain a low-boiling organic solventas the water-soluble organic solvent. Examples of preferred low-boilingorganic solvents usable herein include methanol, ethanol, n-propylalcohol, iso-propyl alcohol, n-butanol, sec-butanol, tert-butanol,iso-butanol, and n-pentanol. Particularly preferred are monohydricalcohols. The low-boiling organic solvent has the effect of shorteningthe drying time of ink.

According to a preferred embodiment of the present invention, the inkcompositions may contain a penetrating agent. Penetrating agents usableherein include various surfactants, such as anionic, cationic, andamphoteric surfactants; alcohols, such as methanol, ethanol, andiso-propyl alcohol; and lower alkyl ethers of polyhydric alcohols, suchas ethylene glycol monomethyl ether, diethylene glycol monoethyl ether,diethylene glycol monobutyl ether, triethylene glycol monobutyl ether,propylene glycol monobutyl ether, and dipropylene glycol monobutylether. In particular, the utilization of diethylene glycol monobutylether or triethylene glycol monobutyl ether is preferred. Although theamount of the penetrating agent added may be properly determined, theamount of the penetrating agent is preferably about 1 to 20% by weight,more preferably about 1 to 10% by weight.

Further, acetylene glycols represented by formula (a) may be mentionedas examples of the penetrating agent.

wherein 0≦m+n≦50; and R¹*, R²*, R³*, and R⁴* each independentlyrepresent an alkyl group, preferably an alkyl group having 1 to 6 carbonatoms.

Commercially available acetylene glycols may be used as the acetyleneglycols represented by the above formula. Specific examples thereofinclude OLFINE Y, Surfynol 82, Surfynol 440, Surfynol 465, and Surfynol485 (all the above products being manufactured by Air Products andChemicals Inc.). In particular, the utilization of Surfynol 465 ispreferred. They may be used alone or in combination of two or more. Theamount of the penetrating agent added is preferably 0.1 to 5% by weight,more preferably 0.3 to 3% by weight.

According to the present invention, the ink composition may furthercontain a saccharide. Specific examples of preferred saccharides includemonosaccharides, disaccharides, oligosaccharides (includingtrisaccharides and tetrasaccharides), and polysaccharides, and preferredexamples thereof include glucose, mannose, fructose, ribose, xylose,arabinose, galactose, aldonic acid, glucitol, sorbit, maltose,cellobiose, lactose, sucrose, trehalose, and maltotriose. Thepolysaccharides refer to saccharides in a wide sense and embracematerials which widely exist in the natural world, such as alginic acid,α-cyclodextrin, and cellulose. Derivatives of these saccharides includereducing sugars of the above saccharides (for example, sugar alcoholsrepresented by the general formula HOCH₂(CHOH)_(n)CH₂OH wherein n is aninteger of 2 to 5), oxidized sugars (for example, aldonic acid anduronic acid), amino acid, and thiosugars. Sugar alcohols areparticularly preferred, and specific examples thereof include maltitoland sorbit.

The ink compositions according to the present invention may furthercontain nozzle clogging preventives, preservatives, antioxidants,electric conductivity adjustors, pH adjustors, solubilizers, viscositymodifiers, penetrating accelerators, surface tension modifiers and thelike.

Examples of preservatives or antimolds include sodium benzoate,pentachlorophenol sodium, 2-pyridinethiol-1-oxide sodium, sodiumsorbate, sodium dehydroacetate, and 1,2-dibenzothiazolin-3-one (ProxelCRL, Proxel BDN, Proxel GXL, Proxel XL-2, and Proxel TN, manufactured byICI).

Examples of pH adjustors, solubilizers, or antioxidants include: amines,such as diethanolamine, triethanolamine, propanolamine, and morpholine,and modification products thereof; inorganic salts, such as potassiumhydroxide, sodium hydroxide, and lithium hydroxide; ammonium hydroxide;quaternary ammonium hydroxides, such as tetramethylammonium; salts ofcarbonic acid, such as potassium carbonate, sodium carbonate, andlithium carbonate; salts of phosphoric acid, such as potassiumphosphate, sodium phosphate, and lithium phosphate;N-methyl-2-pyrrolidone; urea compounds, such as urea, thiourea, andtetramethylurea; allophanates, such as allophanate and methylallophanate; biurets, such as biuret, dimethylbiuret, andtetramethylbiuret; and L-ascorbic acid and salts thereof.

The ink compositions according to the present invention may furthercontain an antioxidant and an ultraviolet absorber, and examples thereofinclude: Tinuvin 328, Tinuvin 900, Tinuvin 1130, Tinuvin 384, Tinuvin292, Tinuvin 123, Tinuvin 144, Tinuvin 622, Tinuvin 770, Tinuvin 292,Irgacor 252, Irgacor 153, Irganox 1010, Irganox 1076, Irganox 1035, andIrganox MD 1024, manufactured by Ciba-Geigy; and lanthanide oxides.

Surface tension modifiers include: alcohols, such as diethanolamine,triethanolamine, glycerin, and diethylene glycol; and nonionic,cationic, anionic, or amphoteric surfactants.

Further, in the present invention, a single optional ingredient may beused as the optional ingredient. Alternatively, a plurality of optionalingredients may be selected from an identical group of optionalingredients or a plurality of groups of optional ingredients and used asa mixture.

In the present invention, the amounts of all the ingredientsconstituting the ink composition are preferably selected so that theviscosity of the ink composition is less than 10 mPa.s at 20° C.

Recording Method

The ink compositions according to the present invention are used inrecording methods wherein ink compositions are deposited on recordingmedia to perform printing.

According to a further aspect of the present invention, there isprovided an ink jet recording method comprising the steps of: ejectingdroplets of the ink composition according to the present invention; anddepositing the droplets onto a recording medium to perform printing.

Further, according to the present invention, there is also provided arecord produced by any one of these recording methods.

EXAMPLES

The present invention will be described in more detail with reference tothe following examples, though it is not limited by these examples only.In the following examples, “%” is by weight unless otherwise specified.

Examination of Fading Rate of Colorants

For colorants listed in Table 1, ink compositions were preparedaccording to the following formulations. For each of the inkcompositions thus obtained, a color patch was printed by means of an inkjet printer PM-770C manufactured by Seiko Epson Corp. in such a mannerthat the amount of ink deposited was regulated so as for the OD value ofeach color to be 1.0.

Ink composition Colorant 2 wt % Styrene-acrylic acid copolymer(dispersant; only when colorant was pigment) 1 wt % Surfynol 465 1 wt %Glycerin (viscosity modifier) q.s. Pure water Balance

The viscosity of each of the ink compositions was modified to 4 mPa.s(20° C.).

The color patches produced for the respective ink compositions wereexposed to light by an acceleration tester under the followingconditions to measure the time (light exposure time) necessary for theOD value of the color patch to be lowered to 0.9 (fading rate 10%).

Acceleration tester: Xenon weather-o-meter Ci35A, manufactured by ATLAS

Optical filter: Borosilicate glass

Irradiation energy: 0.35 W/m²

Black panel temp.: 63° C.

Internal temp. of tester: 24° C.

Internal humidity of tester: 60%

The results were as summarized in Table 1.

TABLE 1 Colorant Light exposure time, hr C.I. Pigment Blue 15:3 1,000C.I. Pigment Blue 15:4 950 C.I. Pigment Red 122 1,100 C.I. Pigment Red202 800 C.I. Pigment Red 209 900 C.I. Pigment Yellow 128 850 C.I.Pigment Yellow 13 100 C.I. Pigment Yellow 17 120 C.I. Pigment Yellow 74300 C.I. Direct Yellow 86 50 C.I. Direct Yellow 132 80 C.I. Acid Yellow23 10

Preparation of Ink Compositions

The following ink compositions were prepared by a conventional method.Specifically, the colorants, together with the dispersant, weredispersed. Other ingredients were then added to and mixed with thedispersion. Insolubles having a size larger than a given size wasremoved from the mixture by filtration. Thus, ink compositions wereprepared. The ink compositions thus obtained were combined to prepareink sets.

Example 1 Ink set 1

Cyan ink composition C.I. Pigment Blue 15:3 2 wt % C.I. Pigment Yellow74 0.01 wt % Styrene-acrylic acid copolymer ½ (dispersant) (ratio tocolorant) Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt %Surfynol 465 1 wt % Diethylene glycol (viscosity modifier) q.s. Purewater Balance The viscosity of the ink composition was modified to 5mPa.s (20° C.). Magenta ink composition C.I. Pigment Red 122 3 wt % C.I.Direct Yellow 86 0.03 wt % Styrene-acrylic acid copolymer ½ (dispersant)(ratio to colorant) Glycerin 15 wt % Triethylene glycol monobutyl ether5 wt % Surfynol 465 1 wt % Diethylene glycol (viscosity modifier) q.s.Pure water Balance The viscosity of the ink composition was modified to5 mPa.s (20° C.). Yellow ink composition C.I. Pigment Yellow 128 4 wt %Styrene-acrylic acid copolymer ½ (dispersant) (ratio to colorant)Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt % Surfynol 4651 wt % Diethylene glycol (viscosity modifier) q.s. Pure water BalanceThe viscosity of the ink composition was modified to 5 mpa.s (20° C.).Black ink composition Carbon black 3 wt % Styrene-acrylic acid copolymer½ (dispersant) (ratio to colorant) Glycerin 15 wt % Triethylene glycolmonobutyl ether 5 wt % Surfynol 465 1 wt % Diethylene glycol (viscositymodifier) q.s. Pure water Balance The viscosity of the ink compositionwas modified to 5 mpa.s (20° C.).

Example 2 Ink Set 2

Cyan ink composition C.I. Pigment Blue 15:3 2 wt % C.I. Pigment Yellow74 0.01 wt % Styrene-acrylic acid copolymer ½ (dispersant) (ratio tocolorant) Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt %Surfynol 465 1 wt % Diethylene glycol (viscosity modifier) q.s. Purewater Balance The viscosity of the ink composition was modified to mPa.s(20° C.). Magenta ink composition C.I. Pigment Red 122 3 wt % C.I.Pigment Yellow 13 0.03 wt % Styrene-acrylic acid copolymer ½(dispersant) (ratio to colorant) Glycerin 15 wt % Triethylene glycolmonobutyl ether 5 wt % Surfynol 465 1 wt % Diethylene glycol (viscositymodifier) q.s. Pure water Balance The viscosity of the ink compositionwas modified to mPa.s (20° C.). Yellow ink composition C.I. PigmentYellow 128 4 wt % Styrene-acrylic acid copolymer ½ (dispersant) (ratioto colorant) Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt %Surfynol 465 1 wt % Diethylene glycol (viscosity modifier) q.s. Purewater Balance The viscosity of the ink composition was modified to 5mPa.s (20° C.). Black ink composition Carbon black 3 wt %Styrene-acrylic acid copolymer ½ (dispersant) (ratio to colorant)Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt % Surfynol 4651 wt % Diethylene glycol (viscosity modifier) q.s. Pure water BalanceThe viscosity of the ink composition was modified to 5 mpa.s (20° C.).

Example 3 Ink Set 3

Cyan ink composition C.I. Pigment Blue 15:3 2 wt % C.I. Pigment Yellow13 0.01 wt % C.I. Pigment Yellow 17 0.01 wt % Styrene-acrylic acidcopolymer ½ (dispersant) (ratio to colorant) Glycerin 15 wt %Triethylene glycol monobutyl ether 5 wt % Surfynol 465 1 wt % Diethyleneglycol (viscosity modifier) q.s. Pure water Balance The viscosity of theink composition was modified to mPa.s (20° C.). Magenta ink compositionC.I. Pigment Red 122 3 wt % C.I. Acid Yellow 23 0.2 wt % Styrene-acrylicacid copolymer ½ (dispersant) (ratio to colorant) Glycerin 15 wt %Triethylene glycol monobutyl ether 5 wt % Surfynol 465 1 wt % Diethyleneglycol (viscosity modifier) q.s. Pure water Balance The viscosity of theink composition was modified to mPa.s (20° C.). Light cyan inkcomposition C.I. Pigment Blue 15:3 0.5 wt % C.I. Pigment Yellow 170.0075 wt % Styrene-acrylic acid copolymer ½ (dispersant) (ratio tocolorant) Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt %Surfynol 465 1 wt % Diethylene glycol (viscosity modifier) q.s. Purewater Balance The viscosity of the ink composition was modified to mPa.s(20° C.). Light magenta ink composition C.I. Pigment Red 122 0.5 wt %C.I. Direct Yellow 132 0.025 wt % Styrene-acrylic acid copolymer ½(dispersant) (ratio to colorant) Glycerin 15 wt % Triethylene glycolmonobutyl ether 5 wt % Surfynol 465 1 wt % Diethylene glycol (viscositymodifier) q.s. Pure water Balance The viscosity of the ink compositionwas modified to mPa.s (20° C.). Yellow ink composition C.I. PigmentYellow 128 4 wt % Styrene-acrylic acid copolymer ½ (dispersant) (ratioto colorant) Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt %Surfynol 465 1 wt % Diethylene glycol (viscosity modifier) q.s. Purewater Balance The viscosity of the ink composition was modified to mPa.s(20° C.). Black ink composition Carbon black 3 wt % Styrene-acrylic acidcopolymer ½ (dispersant) (ratio to colorant) Glycerin 15 wt %Triethylene glycol monobutyl ether 5 wt % Surfynol 465 1 wt % Diethyleneglycol (viscosity modifier) q.s. Pure water Balance The viscosity of theink composition was modified to 5 mPa.s (20° C.).

Example 4 Ink Set 4

Cyan ink composition C.I. Pigment Blue 15:3 2 wt % C.I. Pigment Yellow13 0.01 wt % C.I. Pigment Yellow 17 0.01 wt % Styrene-acrylic acidcopolymer ½ (dispersant) (ratio to colorant) Glycerin 15 wt %Triethylene glycol monobutyl ether 5 wt % Surfynol 465 1 wt % Diethyleneglycol (viscosity modifier) q.s. Pure water Balance The viscosity of theink composition was modified to mPa.s (20° C.). Magenta ink compositionC.I. Pigment Red 122 3 wt % C.I. Acid Yellow 23 0.2 wt % Styrene-acrylicacid copolymer ½ (dispersant) (ratio to colorant) Glycerin 15 wt %Triethylene glycol monobutyl ether 5 wt % Surfynol 465 1 wt % Diethyleneglycol (viscosity modifier) q.s. Pure water Balance The viscosity of theink composition was modified to mPa.s (20° C.). Light cyan inkcomposition C.I. Pigment Blue 15:4 0.5 wt % C.I. Pigment Yellow 170.0075 wt % Styrene-acrylic acid copolymer ½ (dispersant) (ratio tocolorant) Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt %Surfynol 465 1 wt % Diethylene glycol (viscosity modifier) q.s. Purewater Balance The viscosity of the ink composition was modified to 5mPa.s (20° C.). Light magenta ink composition C.I. Pigment Red 122 0.4wt % C.I. Pigment Red 202 0.2 wt % C.I. Direct Yellow 132 0.025 wt %Styrene-acrylic acid copolymer ½ (dispersant) (ratio to colorant)Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt % Surfynol 4651 wt % Diethylene glycol (viscosity modifier) q.s. Pure water BalanceThe viscosity of the ink composition was modified to 5 mPa.s (20° C.).Yellow ink composition C.I. Pigment Yellow 128 4 wt % Styrene-acrylicacid copolymer ½ (dispersant) (ratio to colorant) Glycerin 15 wt %Triethylene glycol monobutyl ether 5 wt % Surfynol 465 1 wt % Diethyleneglycol (viscosity modifier) q.s. Pure water Balance The viscosity of theink composition was modified to 5 mPa.s (20° C.). Black ink compositionCarbon black 3 wt % Styrene-acrylic acid copolymer ½ (dispersant) (ratioto colorant) Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt %Surfynol 465 1 wt % Diethylene glycol (viscosity modifier) q.s. Purewater Balance The viscosity of the ink composition was modified to 5mPa.s (20° C.).

Example 5 (Comparative) Ink Set 5

Cyan ink composition C.I. Pigment Blue 15:3 2 wt % Styrene-acrylic acidcopolymer ½ (dispersant) (ratio to colorant) Glycerin 15 wt %Triethylene glycol monobutyl ether 5 wt % Surfynol 465 1 wt % Diethyleneglycol (viscosity modifier) q.s. Pure water Balance The viscosity of theink composition was modified to 5 mPa.s (20° C.). Magenta inkcomposition C.I. Pigment Red 122 3 wt % Styrene-acrylic acid copolymer ½(dispersant) (ratio to colorant) Glycerin 15 wt % Triethylene glycolmonobutyl ether 5 wt % Surfynol 465 1 wt % Diethylene glycol (viscositymodifier) q.s. Pure water Balance The viscosity of the ink compositionwas modified to 5 mPa.s (20° C.). Light cyan ink composition C.I.Pigment Blue 153 0.5 wt % Styrene-acrylic acid copolymer ½ (dispersant)(ratio to colorant) Glycerin 15 wt % Triethylene glycol monobutyl ether5 wt % Surfynol 465 1 wt % Diethylene glycol (viscosity modifier) q.s.Pure water Balance The viscosity of the ink composition was modified to5 mPa.s (20° C.). Light magenta ink composition C.I. Pigment Red 122 0.5wt % Styrene-acrylic acid copolymer ½ (dispersant) (ratio to colorant)Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt % Surfynol 4651 wt % Diethylene glycol (viscosity modifier) q.s. Pure water BalanceThe viscosity of the ink composition was modified to 5 mPa.s (20° C.).Yellow ink composition C.I. Pigment Yellow 128 4 wt % Styrene-acrylicacid copolymer ½ (dispersant) (ratio to colorant) Glycerin 15 wt %Triethylene glycol monobutyl ether 5 wt % Surfynol 465 1 wt % Diethyleneglycol (viscosity modifier) q.s. Pure water Balance The viscosity of theink composition was modified to 5 mPa.s (20° C.). Black ink compositionCarbon black 3 wt % Styrene-acrylic acid copolymer ½ (dispersant) (ratioto colorant) Glycerin 15 wt % Triethylene glycol monobutyl ether 5 wt %Surfynol 465 1 wt % Diethylene glycol (viscosity modifier) q.s. Purewater Balance The viscosity of the ink composition was modified to 5mPa.s (20° C.).

Evaluation Test

Evaluation Test on Lightfastness of Ink Compositions

The ink sets 1 and 2 were used with an ink jet printer PM-900Cmanufactured by Seiko Epson Corp., and the ink sets 3 and 4 were usedwith an ink jet printer PM-770C manufactured by Seiko Epson Corp. toperform printing under the following conditions.

Printing paper: gloss film manufactured by Seiko Epson Corp.

Printing mode: resolution 720 dpi×720 dpi

Printing pattern: blotted image (100% duty) (printing was carried outfor each ink composition included in the ink set)

Blotted image prints were exposed under the following conditions.

Optical filter: Borosilicate glass

Irradiation energy: 0.35 w/m² (340 nm)

Black panel temp.: 63° C.

Internal temp. of tester: 24° C.

Internal humidity of tester: 60%

Light exposure: 100 kJ/m² (79 hr)

For the prints before and after the exposure, the L*a*b* color system ofthe color difference indication method specified in CIE (CommissionInternational de l'Eclairage) was measured with Macbeth CE-7000spectrophotometer manufactured by Machbeth, and a change in hue ΔE wascalculated by equation

 ΔE=(ΔL ^(*2) +Δa ^(*2) +Δb ^(*2))^(½)

ΔE values can be evaluated as follows.

ΔE≦3: good

3<ΔE≦5: practically acceptable

5<ΔE: practically not acceptable

The results were as summarized in Table 2.

Evaluation Test on Lightfastness of Printed Images

Printing was carried out in the same manner as described above inconnection with the evaluation test on lightfastness of the inkcomposition, except that the following print pattern was printed.

Printing pattern: portrait image (color image)

Images thus obtained were allowed to stand indoors at a place exposed todirect sunlight for one month. The images before and after the standingwere visually inspected by 50 evaluators to determine the number ofevaluators who could perceive a change in hue of image between beforeand after the standing. The lightfastness of images produced by the inksets according to the present invention were evaluated according to thefollowing criteria.

A: Less than 25 evaluators could perceive a change in hue of image.

B: Not less than 25 evaluators could perceive a change in hue of image.

The results were as summarized in Table 2.

TABLE 2 Ink Ink Ink Ink Ink set 1 set 2 set 3 set 4 set 5 ΔE Cyan ink1.0 0.8 1.2 1.2 5.3 Magenta ink 1.8 1.7 2.0 2.0 7.2 Light cyan ink — —0.5 0.3 3.1 Light magenta ink — — 0.7 0.4 4.6 Evaluation oflightfastness A A A A B of color image

What is claimed is:
 1. A cyan ink composition comprising, as colorants,a cyan colorant selected from the group consisting of C.I. Pigment Blue15:3, C.I. Pigment Blue 15:4, and a mixture of said cyan colorants, anda yellow colorant having a higher fading rate than the cyan colorant. 2.The cyan ink composition according to claim 1, wherein the content ofthe yellow colorant is 0.005 to 0.05% by weight based on the cyancolorant.
 3. A magenta ink composition comprising, as colorants, amagenta colorant selected from the group consisting of C.I. Pigment Red122, C.I. Pigment Red 202, C.I. Pigment Red 209, and mixtures of saidmagenta colorants, and a yellow colorant having a higher fading ratethan the magenta colorant.
 4. The magenta ink composition according toclaim 3, wherein the content of the yellow colorant is 0.005 to 0.05% byweight based on the magenta colorant.
 5. The ink composition accordingto claim 1, wherein the yellow colorant is a dye.
 6. The ink compositionaccording to claim 5, wherein the dye is selected from the groupconsisting of C.I. Acid Yellow 23, C.I. Direct Yellow 86, C.I. DirectYellow 132, and mixtures of said dyes.
 7. The ink composition accordingto claim 1, which is used in an ink jet recording method.
 8. An ink setcomprising a yellow ink composition, a magenta ink composition, and acyan ink composition, said cyan ink composition being the inkcomposition according to claim
 1. 9. An ink set comprising a yellow inkcomposition, said magenta ink composition being the ink compositionaccording to claim
 3. 10. An ink set comprising a yellow inkcomposition, a magenta ink composition, and a cyan ink composition, saidcyan ink composition being the ink composition according to claim 1,said magenta ink composition being the ink composition according toclaim
 3. 11. The ink set according to claim 8, which further comprises ablack ink composition.
 12. The ink set according to claim 8, which isused in an ink jet recording method.
 13. A recording method comprisingthe step of depositing an ink composition onto a recording medium toperform printing, said ink composition being one according to claim 1.14. An ink jet recording method comprising the steps of: ejectingdroplets of an ink composition; and depositing the droplets onto arecording medium to perform printing, said ink composition being oneaccording to claim
 1. 15. A record produced by the method according toclaim
 13. 16. The ink composition according to claim 2, wherein theyellow colorant is a dye.
 17. The ink composition according to claim 3,wherein the yellow colorant is a dye.
 18. The ink composition accordingto claim 4, wherein the yellow colorant is a dye.
 19. The inkcomposition according to claim 2, which is used in an ink jet recordingmethod.
 20. The ink composition according to claim 3, which is used inan ink jet recording method.